1. Field of the Invention
The present invention relates to a stator for an alternator, and, in particular, to a stator for an alternator including a plurality of turn portions which are bent back in a similar shape inclined with respect to an outer circumferential surface of a stator core and so as to align in rows in a circumferential direction and form coil end groups, and to a method for manufacturing the same
2. Description of the Related Art
FIG. 29 is a perspective view showing a coil end of a stator of a conventional automotive alternator described in, for example, Japanese Patent Publication 2927288. In coil ends of a stator coil constructed as above, when attempting to lower a height of the coil ends, since the conductors are rectangular in cross section at turn portions of the coil ends, adjacent conductors contact one another at corner portions thereof and damage an insulating coating, and further cause a short-circuit. Thus, there has been a problem in that (the height of) the coil ends could not be lowered.
Moreover, it is necessary to arrange the turn portions of the coil ends as adjacent conductors, and there is a problem in that during the bending process conductors interfere with one another at the turn portions due to irregularities in the bending process.
FIG. 30 is a perspective view showing a stator coil of a conventional automotive alternator described in Japanese Patent Application Laid-open No. Sho 63-194543. In this conventional example, in a stator coil provided in a stator and installed in a plurality of slots, after installing conductors of a circular cross section in slots, the cross sections are pressure formed into approximately rectangular shapes and the space factor is improved. However, since the winding method for this sort of stator coil is concentrated winding in which a plurality of turns of winding are made in succession in similar teeth, the stator coil does not include (turn portion) which are bent back in a similar shape so as to be inclined with respect to an outer circumferential surface of a stator core and so as to line up in rows in a circumferential direction and form a plurality of coil ends, and no particular effects are achieved by the roughly circular cross-sectional shape of the turn portions.
The conventional stator for an alternator shown in FIG. 29 exhibits the following problems, namely:
since the conductors have a rectangular cross section at the turn portions of the coil ends, adjacent conductors contact one another at corner portions thereof and damage an insulating coating, and further cause a short-circuit, hence, (the height of) the coil ends cannot be lowered;
it is necessary to arrange the turn portions of the coil ends as adjacent conductors, and during the bending process conductors interfere with one another at the turn portions due to irregularities in the bending process;
the axial dimension of the stator is increased because the height of the coil ends cannot be decreased;
since the height of the coil ends cannot be decreased, the length of the coil is increased and the resistance thereof increases, output is reduced during power generation, and an increase in generated heat is incurred;
since the height of the coil ends cannot be decreased, coil end leakage inductance increases and output is reduced;
since the height of the coil ends cannot be decreased, the length of the conductor is increased and the cost of the copper wire material increases;
since the height of the coil ends cannot be decreased, the ventilating resistance of the cooling air increases and cooling characteristics are degraded; and
since the height of the coil ends cannot be decreased, the flow of the cooling air is disturbed (made turbulent) by the coil ends and wind noise increases.
The present invention aims to solve the above problems with the conventional art and an object of the present invention is to provide a stator for an alternator, and method for manufacturing the same, in which: it is possible to increase a space factor of a stator coil in slots and increase a cross-sectional area of the stator coil and thus, a resistance of the stator coil may be reduced and an output voltage increased; it is possible to increase a thickness of stator teeth and thus, magnetic resistance of magnetic flux interlinking the stator coil may be reduced, and further, since magnetic flux density is reduced such that is difficult for magnetic saturation to occur, output may be increased; furthermore, since it is made difficult for conductors to interfere with one another at coil ends, a height of the coils ends may be reduced and the size of the entire alternator may also be reduced; since it is possible to reduce the height of the coil ends, coil resistance and coil end leakage inductance may be reduced and output may be increased; further, because an amount of material may be reduced, it is possible to lower the cost; also, even in the case where conductors contact one another, since the conductors are of an approximately circular cross section with a large radius of curvature, the contact stress is small and it is difficult for the insulating coating to become damaged; moreover, because a cross section of an intersecting portion of adjacent coil ends is roughly circular, it is difficult for forming irregularities to cause a difference in shape in the coil ends and the forming of the coil is simplified.
In order to achieve the above object, according to one aspect of the present invention, there is provided,
a stator for an alternator comprising:
a stator core fixed to a case and facing a rotor, and formed in a circumferential direction with a number of radially extending slots of a rectangular cross section; and a stator coil installed in the slots of the stator core; and
the stator coil comprising wire-shaped conductors wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots, the conductors being bent back outside the slots at axial end surfaces of the stator core to form a plurality of turn portions, the plurality of turn portions being bent back in a similar shape inclined with respect to an outer circumferential surface of the stator core and so as to align in rows in a circumferential direction and form coil end groups, and, a cross-section of at least a principal portion of the stator coil inside the slots is approximately rectangular, a cross-section of at least a portion including end portions of the coil ends is approximately circular or approximately elliptic, and a cross-sectional area of the approximately rectangular cross-sectional portion differs from that of the approximately circular cross-sectional portion or the approximately elliptic cross-sectional portion.
According to another aspect of the present invention there is provided a stator for an alternator wherein:
a cross section the conductors comprising the coil ends is approximately circular or approximately elliptic throughout a substantial entirety of the conductors.
According to yet another aspect of the present invention there is provided a stator for an alternator wherein:
a cross-sectional area of the conductors inside the slots is larger than a cross-sectional area of the conductors comprising the coil ends.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
the stator coil comprises a plurality of U-shaped conductor segments, end portions thereof being joined to each other, and a cross section of at least a portion including ends of turn portions of the U-shaped conductor segments is approximately circular or approximately elliptic.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
a cross section of end portions of the U-shaped conductor segments is approximately circular or approximately elliptic.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
the stator coil comprises a continuous conductor wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots, the conductor being bent back outside the slots at both sides of the stator core.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
a plurality of the conductors are disposed in a radial direction of the slots, and a cross section of the conductors in the slots is an approximately rectangular shape having long sides in a radial direction.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
the conductors comprise four (4) or more layers in the slots, and the stator coil comprises two (2) or more rows of coil end groups.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
a hardness of the conductors of the coil ends is less than that of the conductors in the slots.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
the rotor further comprises a air-cooling fan being rotationally driven together with the rotor.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
a varnish or resin is applied to the coil end groups.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
portions corresponding to coil ends in conductors of an approximately rectangular cross section throughout are pressed and made to an approximately circular cross section or approximately elliptic cross section.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
portions of conductors of an approximately circular cross section throughout installed in the slots are pressed and made to an approximately rectangular cross section.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
portions of conductors installed in the slots are pressed so as to make a cross-sectional area thereof larger than a cross-sectional area of conductors of the coil ends.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
portions of conductors of an approximately circular cross section throughout are installed in the slots and pressed to an approximately rectangular cross section.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
only portions of conductors of an approximately circular cross section throughout installed in the slots are changed to a wave shape, after which the wave shape portion is pressed to an approximately rectangular cross section.
According to still yet another aspect of the present invention there is provided a stator for an alternator wherein:
portions of conductors of an approximately circular cross section throughout installed in the slots are changed into a shape of large cross section and then pressed to an approximately rectangular cross section.
According to still yet another aspect of the present invention there is provided a method of manufacturing a stator for an alternator including,
in a stator for an alternator comprising:
a stator core fixed to a case and facing a rotor, and formed in a circumferential direction with a number of radially extending slots of a rectangular cross section; and a stator coil installed in the slots of the stator core; and
the stator coil comprising wire-shaped conductors wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots, the conductors being bent back outside the slots at axial end surfaces of the stator core to form a plurality of turn portions, the plurality of turn portions being bent back in a similar shape inclined with respect to an outer circumferential surface of the stator core and so as to align in rows in a circumferential direction and form coil end groups, and, a cross-section of at least a principal portion of the stator coil inside the slots is approximately rectangular, a cross-section of at least a portion including end portions of the coil ends is approximately circular or approximately elliptic, and a cross-sectional area of the approximately rectangular cross-sectional portion differs from that of the approximately circular cross-sectional portion or the approximately elliptic cross sectional portion,
a circular shape forming process for pressing portions corresponding to coil ends in the conductors of an approximately rectangular cross section throughout into an approximately circular cross section or approximately elliptic cross section.
According to still yet another aspect of the present invention there is provided a method of manufacturing a stator for an alternator including,
in a stator for an alternator comprising:
a stator core fixed to a case and facing a rotor, and formed in a circumferential direction with a number of radially extending slots of a rectangular cross section; and a stator coil installed in the slots of the stator core; and
the stator coil comprising wire-shaped conductors wound so as to alternately occupy an inner layer and an outer layer in a slot depth direction within the slots at intervals of a predetermined number of slots, the conductors being bent back outside the slots at axial end surfaces of the stator core to form a plurality of turn portions, the plurality of turn portions being bent back in a similar shape inclined with respect to an outer circumferential surface of the stator core and so as to align in rows in a circumferential direction and form coil end groups, and, a cross-section of at least a principal portion of the stator coil inside the slots is approximately rectangular, a cross-section of at least a portion including end portions of the coil ends is approximately circular or approximately elliptic, and a cross-sectional area of the approximately rectangular cross-sectional portion differs from that of the approximately circular cross-sectional portion or the approximately elliptic cross-sectional portion,
a rectangular shape forming process for pressing portions of conductors of an approximately circular cross section throughout to be installed in the slots into an approximately rectangular cross section.
According to still yet another aspect of the present invention there is provided a method of manufacturing a stator coil for an alternator wherein:
the rectangular shape forming process presses portions of the conductors installed in the slots so as to make a cross-sectional area thereof larger than a cross-sectional area of the conductors of the ends.
According to still yet another aspect of the present invention there is provided a method of manufacturing a stator coil for an alternator wherein:
the rectangular shape forming process presses conductors of an approximately circular cross section throughout to an approximately rectangular cross section after the conductors are installed in the slots.
According to still yet another aspect of the present invention there is provided a method of manufacturing a stator coil for an alternator wherein:
in the rectangular shape forming process, only portions of conductors of an approximately circular cross section throughout installed in the slots are processed to a wave shape, after which the wave shape portion is pressed to an approximately rectangular cross section.
According to still yet another aspect of the present invention there is provided a method of manufacturing a stator coil for an alternator wherein:
in the rectangular shape forming process, portions of conductors of an approximately circular cross section throughout installed in the slots are processed into a shape of large cross section and then pressed to an approximately rectangular cross section.